Diverting incoming calls via a specific number (call through)

With the "Call through" function, you can configure your FRITZ!Box so that certain calls are forwarded to any destination number using a cheaper telephone connection. This saves costs compared to using your landline or mobile telephone to call the number directly, for example.

Example:You are on the road and would like to call somebody abroad using your mobile telephone. You can either make an international call, or you can call your FRITZ!Box at home and have it forward the call to the extension abroad over the Internet at a much less expensive rate.

1 Configuring call through

Click on the "Call Through" tab. If the tab is not displayed, enable the Advanced View first.

Enable the option "Enable call through".

From the drop-down list "Incoming Number", select the number that you would like to enable call through for.

From the drop-down list "Number for Outgoing Calls", select the number the FRITZ!Box should use for forwarding calls.

Enter a four-digit number in the "PIN" field in the "Security Settings" section. Callers must enter this PIN on their telephone in order for their call to be forwarded via the FRITZ!Box.

If only certain callers should be allowed to use the call through function, enable the option "Only accept calls from the following numbers" and enter their telephone numbers including the area code.

Important:Authorized callers must transmit their caller ID; otherwise, they cannot use call through.

Click "Apply" to save the settings.

2 Using call through

Call the telephone number that you configured call through for.

After the signal tone, enter the PIN on the telephone.

If you want to have a call routed via the FRITZ!Box:

Enter 0, because "Automatic outside dialing" is disabled for the call through function.

As soon as you hear the ringing tone, enter the destination number and include the area code.

If you would like to call a telephone connected to the FRITZ!Box, enter the internal number of the telephone you would like to call.

Note:You can find the internal numbers of the telephony devices under "Telephone Book > Internal Numbers" in the FRITZ!Box user interface.

3 Problems with establishing a call through connection

If there was a problem with establishing the call through connection, proceed as follows:

Own caller ID is not transmitted

If you have configured "call through" in the FRITZ!Box and then use this function to make a call, your caller ID will not be transmitted automatically. However, you can transmit the telephone number of the telephone line that your FRITZ!Box is connected to on a call-by-call basis (only for one call):

Enter the prefix #31# before entering the telephone number you would like to be routed to.

Important:The number of the telephone line you are calling the FRITZ!Box from cannot be transmitted.

Cannot hear prompt to enter your PIN

If you do not hear the prompt to enter the PIN, then call through was only configured for specific telephone numbers. The telephone number being transmitted to the FRITZ!Box does not match a telephone number you enabled call through for, or your caller ID is not being transmitted. Check the FRITZ!Box's call list to see which caller ID you are transmitting.

PIN entry is not accepted or digits are not / are not recognized correctly

If the PIN is not accepted or one or more digits are not recognized or are not recognized correctly, then inband signaling is being used for the DTMF transmission. With this transmission method, the DTMF tones are transmitted within the voice data stream and not over a separate channel, which leads to errors in recognizing DTMF tones. Therefore, set the DTMF transmission to "SIP-INFO" or "RTP-Event" in the FRITZ!Box:

Select "Other provider" from the drop-down list, even if you are using a pre-configured Internet telephony provider.

For "DTMF transmission", select the setting "INFO, RTP or in-band".

Click "OK" to save the settings.

One or more digit(s) is/are recognized twice

If certain digits are recognized twice, then the SIP INFO or RTP Event method is being used for the DTMF transmission. These are secure transmission methods, but your provider does not cleanly filter the original DTMF spectrum from the actual voice data stream. This causes the DTMF entry to be detected once as in-band and once as the separately transmitted DTMF event. Changing the DTMF transmission to "In-band" may help:

Select "Other provider" from the drop-down list, even if you are using a pre-configured Internet telephony provider.

For "DTMF transmission", select the setting "In-band".

Click "OK" to save the settings.

Busy signal after dialing the number for an outside line

Either a local call is already being conducted or a call through connection is already active. Thus, the maximum number of possible calls over the FRITZ!Box has been reached.

Calls are ended after a long delay

The FRITZ!Box does not detect the busy signal from the party being called, or it detects it too late. End the connection manually as follows:

Enter # or ## on your telephone. A beep will indicate that the call through connection has been cleared, but the connection to the FRITZ!Box remains intact. Now you can either hang up to completely terminate the connection, or you can have the FRITZ!Box forward your call again.